Many hand-held power tools or other outdoor power equipment are powered by electric motors or two-stroke internal combustion engines. Electric motors are limited to certain applications due to the available power for products utilizing a cord, and battery longevity for cordless products. Conventional two-stroke engines include a lubricating means in which the lubricant is mixed with fuel which allows the engines to operate in any given position such as upright, inclined, sideways or upside down. For example, when using a chain saw, the chain saw is typically capable of use in either an upright, sideways or upside down condition. Over the past few years, there has been a requirement by various governing bodies to reduce the emissions associated with all small gas engines, particularly, conventional two-stroke engines. Thus, because four-stroke engines do not require the mixing of lubricant and fuel, it is desirable to use four-stroke engines in place of conventional two-stroke engines, since four-stroke engines normally release fewer undesirable emissions as compared to the amount of undesirable emissions released by conventional two-stroke engines.
However, previously, it was widely viewed that four-stroke internal combustion engines could only be used for limited applications, such as lawn mowers, snowblowers, generators, or other portable products having wheels. It was thought that these prior four-stroke engines were too heavy and cumbersome to be used in operator-carried power tools. Moreover, since it is generally necessary to store oil separate from the gas so that the oil can be used for lubrication, traditional low-cost four-stroke engines were not designed to operate in any position other than a substantially upright position because if the engine was significantly tipped or tilted, the lubricant would foul the engine. Only very recently has it been contemplated that a four-stroke engine may be used in a hand-held power tool or in other applications where the engine may operate in a tipped or tilted condition.